Heterocyclic compounds play an immense role in organic chemistry, especially in active ingredients and pharmaceuticals, and the synthesis of heterocyclic compounds represents an important and steadily growing field of research.
Pyrazoles represent an important class of heterocycles. Pyrazoles occur relatively rarely in natural materials but are an important structural element in biologically active compounds, which in some cases can have great economic importance as pharmaceuticals or plant protecting agents. Two prominent examples are the COX-2 inhibitor Celecoxib, which is used to treat rheumatoid arthritis, and the contact poison Fipronil®, which is effective as a GABA inhibitor against ectoparasites, such as fleas, lice, ticks, and mites.
A Pyrazole-synthesizing process using the coupling of carboxylic acid derivatives and Enamines under oxidative conditions is known from WO 2011/120861. However, the task at hand is to improve this method further.